1. Field of the Invention
The present invention relates to a method for producing a film with a coating, and, in particular, relates to a method for producing a film with a coating, comprising a step of applying a coating liquid onto an inorganic vapor-deposited film deposited on a support in advance.
2. Description of the Related Art
A technique of applying a coating liquid onto a support to produce a film with a coating is widely used in the production field of a functional film such as an optical film.
When a coating liquid for forming a coating and a support have a relationship where they are easily repelling each other, or when the coating liquid and an underlayer formed on a support in advance have a relationship where they are easily repelling each other, however, there is the problem of easily causing coating misses.
Herein, cissing means the formation of small pin hole-shaped pores or depressions due to the fact that the coating liquid is partially repelled and not applied when the coating liquid is applied, or due to the fact that a coating thickness is small. These pore or depression portions are referred to coating misses (coating failure).
Causes for such a mutually easily repelling relationship include: a surface tension of the coating liquid is comparable to a surface free energy of the support; and the surface tension of the coating liquid is larger than the surface free energy of the support. When flowage due to the unevenness in surface tension (Marangoni convection) occurs, cissing more easily occurs as the coating thickness is larger.
When a disturbance such as variation in the surface free energy due to the variation in deposition thickness, is present in an inorganic vapor-deposited film formed as the underlayer, cissing more easily occurs as the coating thickness of the coating liquid applied onto the inorganic vapor-deposited film is thinner or a viscosity of the coating liquid is smaller.
Then, if coating miss portions are present in a functional film such as an optical film, the coating miss portions exert no functional performance and thus the functional film becomes defective.
As a measure for preventing cissing, the addition of a surfactant is generally known to be effective, but there is a problem that the function of a film may be adversely affected if the content of the surfactant is high.
As another measure for preventing cissing, there is a method of sandwiching an intermediate layer or an easily-adhesive layer having a high affinity between the coating and the support, or between the coating and the underlayer. As still another measure, there is a method of subjecting the support to a plasma treatment to improve an affinity of the support, as disclosed in Japanese Patent Application Laid-Open No. 2011-190318, for example.